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  <title>Truncates the file to a given length</title>
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  <div id="layout-content"><div id="splfileobject.ftruncate" class="refentry">
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  <h1 class="refname">SplFileObject::ftruncate</h1>
  <p class="verinfo">(PHP 5 &gt;= 5.1.0, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">SplFileObject::ftruncate</span> &mdash; <span class="dc-title">Truncates the file to a given length</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-splfileobject.ftruncate-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="modifier">public</span> <span class="methodname"><strong>SplFileObject::ftruncate</strong></span>(<span class="methodparam"><span class="type">int</span> <code class="parameter">$size</code></span>): <span class="type">bool</span></div>

  <p class="para rdfs-comment">
   Truncates the file to <code class="parameter">size</code> bytes.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-splfileobject.ftruncate-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>
    
     <dt>
<code class="parameter">size</code></dt>

     <dd>

      <p class="para">
       The size to truncate to.
      </p>
      <blockquote class="note"><p><strong class="note">注意</strong>: 
       <p class="para">
        If <code class="parameter">size</code> is larger than the file it is extended with null bytes.
       </p>
       <p class="para">
        If <code class="parameter">size</code> is smaller than the file, the extra data will be lost.
       </p>
      </p></blockquote>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-splfileobject.ftruncate-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   成功时返回 <strong><code>true</code></strong>， 或者在失败时返回 <strong><code>false</code></strong>。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-splfileobject.ftruncate-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-3715">
    <p><strong>示例 #1 <span class="methodname"><strong>SplFileObject::ftruncate()</strong></span> example</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;Create&nbsp;file&nbsp;containing&nbsp;"Hello&nbsp;World!"<br /></span><span style="color: #0000BB">$file&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">SplFileObject</span><span style="color: #007700">(</span><span style="color: #DD0000">"/tmp/ftruncate"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"w+"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fwrite</span><span style="color: #007700">(</span><span style="color: #DD0000">"Hello&nbsp;World!"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Truncate&nbsp;to&nbsp;5&nbsp;bytes<br /></span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">ftruncate</span><span style="color: #007700">(</span><span style="color: #0000BB">5</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Rewind&nbsp;and&nbsp;read&nbsp;data<br /></span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">rewind</span><span style="color: #007700">();<br />echo&nbsp;</span><span style="color: #0000BB">$file</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fgets</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>以上例程的输出类似于：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Hello
</pre></div>
    </div>
   </div>
  </p>
 </div>


 <div class="refsect1 seealso" id="refsect1-splfileobject.ftruncate-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.ftruncate.html" class="function" rel="rdfs-seeAlso">ftruncate()</a> - 将文件截断到指定的长度</span></li>
   </ul>
  </p>
 </div>


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